OVERVIEW: What every practitioner needs to know

Are you sure your patient has Legg-Perthes disease? What are the typical findings for this disease?

Legg-Perthes disease is a disorder of the hip in children. Although the cause of the disease is unknown, compromise of the vascular supply to the developing femoral head leads to progressive subchondral bone collapse, variable remodeling, and deformity.

Treatment continues to evolve to prevent and correct existing femoral head deformity and hip incongruity.Treatment focuses on maintaining range of motion and a congruent hip. This is accomplished with activity modification, physical therapy, bracing or casting, and surgery directed at femoral head containment within the acetabulum. Containment surgery is best performed early, usually in patients younger than 8 years. Poor results are often seen in children older than 8 years with significant femoral head collapse at the time of diagnosis.

Current research is aimed at the use of a bisphosphonates to reduce changes in the femoral head. Long-term outcomes are variable, with the least deformed and congruent hips exhibiting little symptomatic arthritis.

History:

The ratio of boys-girls is 5:1.

Typical age at onset is 4-12 years, most commonly between 5 and 8 years.

There is a bilateral incidence of 10%-15%.

Children are often hyperactive and small for their age and may exhibit delayed bone age.

Children typically present with painless limp lasting weeks to months. It is often worse with activity or at the end of the day.

Occasionally, there may be history of antecedent trauma.

When there is pain, it is usually mild and activity related. Referred pain is common, often affecting the knee (femoral nerve), medial thigh (obturator nerve), or buttock (sciatic nerve).

Physical Examination:

Hip motion is unaffected in the early stages; however, as the disease progresses, internal rotation and abduction may be limited and can be severely restricted in the later stages. Hip flexion and adduction contractures may develop in extreme cases.

Spasm may occur with log-roll of the lower extremity.

A Trendelenburg or antalgic gait may result from weakness of the abductors and pain, respectively.

Atrophy of the quadricep, gluteal, hamstring, or gastrocnemius muscles may occur late.

Motion often improves as the femoral head reossifies; however, residual deformity may lead to chronic pain, gait abnomality, or limb length discrepancy of 1-2 cm.

Legg-Perthes disease is a diagnosis of exclusion; thus other causes of osteonecrosis must be ruled out.

What other disease/condition shares some of these symptoms?

Multiple epiphyseal dysplasia, spondyloepiphyseal dysplasia, Morquio syndrome; unlike in Legg-Perthes disease, in these conditions skeletal dysplasias are not isolated to the hips and affect other areas of the skeleton

Hypothyroid disease: Thyroid hormone is an important regulator of bone growth and maturation at the level of the physis. Endochondral ossification is directly affected by decreases in thyroid hormone, often leading to delayed growth, short stature, and irregular physes. Bone age is delayed. This directly impacts the formation of the epiphysis and may lead to deformity and an incongruous joint.

Gaucher disease

Infection

What caused this disease to develop at this time?

Genetic: No conclusive evidence exists supporting a genetic influence and the development of Legg-Perthes disease. However, recent published reports of familial bilateral osteonecrosis demonstrate a mutation in type II collagen with radiographic changes similar to those observed in Legg-Perthes disease.

Trauma: The primary blood supply to the femoral head is the ascending branch of the medial circumflex artery. There is a narrow passage for the lateral epiphyseal artery, as it is the primary blood supply to the femoral head.

Vascular abnormalities

Hyperactivity, attention deficit hyperactivity disorder

Coagulopathy: protein C and protein S deficiency

Growth and endocrine abnormalities

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

Laboratory tests are not helpful for confirming the diagnosis.

White blood cell count, erythrocyte sedimentation rate, and C-reactive protein level may be beneficial to rule out infection. The erythrocyte sedimentation rate may be slightly elevated in Legg-Perthes disease.

Would imaging studies be helpful? If so, which ones?

Anteroposterior and frog leg lateral radiographic projections are useful to follow disease progression and aid in disease classification. However, they are not sensitive or specific to demonstrate perfusion to the femoral head.

Gadolinium-enhanced magnetic resonance imaging (MRI) is useful to document vascularity to the femoral head, although routine use to aid in diagnosis, prognosis, and treatment has not been determined.

If you are able to confirm that the patient has Legg-Perthes Disease, what treatment should be initiated?

Treatment is focused on maintaining a spherical and congruent joint.

Nonsurgical management or surgery to realign the joint is based on two long-term prospective study groups that assessed outcomes in patients with Legg-Perthes disease. The Perthes Study Group and the Norwegian Perthes Study provide the highest level of evidence (level II) on the treatment of Legg-Perthes disease.

The Perthes Study Group demonstrated outcomes correlated with age at disease onset and the lateral pillar classification. Patients younger than 8 years of age with a group B lateral patellar classification did well regardless of treatment. Surgery is recommended in patients older than 8 years with a group B or B/C lateral patellar classification. Patients whose hips had a group C lateral patellar classification did poorly irrespective of age or treatment.

The Norwegian Perthes study demonstrated similar findings. Hips with less than 50% head involvement responded wellto treatment regardless of patient age at onset or treatment. Unlike like the Perthes Study Group, hips with a group B lateral pillar showed no difference with respect to age. Patients older than 6 years with more than 50% head involvement demonstrated significantly improved outcomes with surgery.

Both study groups recommend no surgical treatment in children younger than 6 years.

Nonsurgical treatment is variable, consisting of bed rest followed by range of motion and abductor stretching, use of nonsteroidal antiinflammatory agents, and abduction bracing or casting. Bisphosphonates appear to provide improved results in animal models; however few clinical studies demonstrate their efficacy and therefore are not included in the standard treatment algorithm.

Surgical treatment, including femoral and/or pelvic osteotomies, are designed to contain the femoral head in a congruent acetabulum. Little evidence exists about which specific osteotomy is best; however it appears that a proximal femoral osteotomy with or without an acetabular osteotomy provides the best results.

What are the adverse effects associated with each treatment option?

Conservative treatment may lead to limited joint motion, poor femoral head coverage, and an incongruous joint despite patient compliance.

Surgical treatment presents typical risks such as infection, bleeding, neurovascular injury, nonunion, hardware failure, limited joint motion, and pain. Femoroacetabular procedures designed to improve femoral head coverage and a congruent joint may lead to a Trendelenburg gait secondary to greater trochanteric overgrowth and abductor weakness, and femoroacetabular impingement, which may require future surgical intervention.

Residual femoral head and acetabular deformity may lead to significant pain and early arthrosis.

What are the possible outcomes of Legg-Perthes disease?

Long-term studies have shown that most patients remain asymptomatic despite obvious femoral head deformity. There are a few long-term studies, and those that exist are limited by small patient size, lateral follow-up, and patients treated nonoperatively.

Long-term hip function has been shown to deteriorate, with some patients requiring total hip arthroplasty, complaining of disabling pain, and poor function according to the Iowa Hip Score.

Patients diagnosed and treated before age 6 years achieve good results (50%-80%) radiographically and clinically. No significant difference has been demonstrated between treatment modalities. Surgical treatment has not been shown to be of additional benefit; therefore patients less than 6 years of age are best treated nonoperatively.

Treatment for patients age 6-8 years is less clear. Only two conflicting studies exist demonstrating a difference between conservative and operative treatment. Recommendations are difficult and should be determined on a case-by-case basis.

Femoral osteotomy has been shown to be beneficial in patients older than 8 years when femoral head collapse is greater than 50%. This may require an acetabular procedure for improved coverage and an epiphysiodesis of the greater trochanter to minimize the development of a Trendelenburg gait.

What causes this disease and how frequent is it?

The cause of Legg-Perthes disease is unknown. Age of onset is commonly between 4 and 8 years; however, the range is 2-12 years. It is four times more common in boys than in girls.

There is a higher risk in children of short stature, delayed bone age, and a diagnosis of hyperactivity disorders. It is rare in chldren of African descent. There is a higher risk in children exposed to second-hand smoke and those of lower socioeconomic status.

Little evidence exists supporting a genetic cause for Legg-Perthes disease. Two recent studies identified mutations in the type II collagen gene. The changes in the femoral head were similar to radiographic findings observed in Legg-Perthes disease.

How do these pathogens/genes/exposures cause the disease?

It is unclear how specific factors cause or affect the disease.

What complications might you expect from the disease or treatment of the disease?

Pain

Limp

Limited hip motion

Arthrosis

Are additional laboratory studies available; even some that are not widely available?

Laboratory studies are not typically indicated.

How can this disease be prevented?

There is no prevention for Legg-Perthes disease, as the cause has yet to be identified.

Ongoing controversies regarding etiology, diagnosis, treatment

The cause of Legg-Perthes disease remains unclear. Current research is investigating the pattern of blood flow throughout the disease process, which may possibly lead to a prognostic tool, such as MRI, that may facilitate treatment decisions.

Treatment in the child older than age 7 years continues to be examined, as no surgical treatment has been demonstrated to significantly impact the development of a normal hip at skeletal maturity.